This invention relates to performance monitoring of gas-phase air filters.
Performance monitoring of gas-phase air filters is particularly important in many environments, including semiconductor fabrication clean environments, museums, archives, petrochemical plants, refineries, wastewater treatment facilities, airport terminals, office buildings in urban areas, and hospitals. For example, the presence of even low levels of corrosive gases and vapors threatens cultural property and capital equipment including computer control systems, manufacturing tools, electrical systems, and facility mechanical equipment. The performance of gas-phase air filters used in these environments must be monitored to determine when the filters are not filtering at acceptable levels and should be replaced.
Air filtering is critical within an environment that must remain clean, such as a semiconductor device manufacturing environment (cleanroom), which is sensitive to low levels of gas-phase (molecular) contamination. Examples of process-limiting molecular contaminants include: acids, such as hydrochloric acid, nitric acid, phosphoric acid, hydrobromic acid; bases, such as ammonia, ammonium hydroxide, tetramethylammonium hydroxide, trimethylamine, triethylamine, hexamethyldisilazane, NMP, cyclohexylamine, diethylaminoethanol, methylamine, dimethylamine, ethanolamine, morpholine, condensables, such as silicones and hydrocarbons with a boiling point greater than or equal to 150.degree. C.; and dopants, such as boron (usually as boric acid), phosphorus (usually as organophosphate), and arsenic (usually as arsenates).
Performance monitoring of gas-phase air filters is also particularly important in areas where even low concentration levels of toxic gases and irritants threaten health and safety of people. Proper monitoring is important to ensure timely filter replacement to maintain necessary air cleanliness.